linux-kernel - [RFC 2/4] io_uring: frame out futex op

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Date:   Tue,  1 Jun 2021 15:58:27 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     io-uring@...r.kernel.org
Cc:     Jens Axboe <axboe@...nel.dk>, Andres Freund <andres@...razel.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Darren Hart <dvhart@...radead.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        linux-kernel@...r.kernel.org
Subject: [RFC 2/4] io_uring: frame out futex op

Add userspace futex request definitions and draft some internal
functions.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 fs/io_uring.c                 | 23 +++++++++++++++++++++++
 include/uapi/linux/io_uring.h |  9 +++++++++
 2 files changed, 32 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index fc9325472e8d..2c6b14a3a4f6 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -77,6 +77,7 @@
 #include <linux/splice.h>
 #include <linux/task_work.h>
 #include <linux/pagemap.h>
+#include <linux/futex.h>
 #include <linux/io_uring.h>
 
 #define CREATE_TRACE_POINTS
@@ -665,6 +666,10 @@ struct io_unlink {
 	struct filename			*filename;
 };
 
+struct io_futex {
+	struct file			*file;
+};
+
 struct io_completion {
 	struct file			*file;
 	struct list_head		list;
@@ -809,6 +814,7 @@ struct io_kiocb {
 		struct io_shutdown	shutdown;
 		struct io_rename	rename;
 		struct io_unlink	unlink;
+		struct io_futex		futex;
 		/* use only after cleaning per-op data, see io_clean_op() */
 		struct io_completion	compl;
 	};
@@ -1021,6 +1027,7 @@ static const struct io_op_def io_op_defs[] = {
 	},
 	[IORING_OP_RENAMEAT] = {},
 	[IORING_OP_UNLINKAT] = {},
+	[IORING_OP_FUTEX] = {},
 };
 
 static bool io_disarm_next(struct io_kiocb *req);
@@ -5865,6 +5872,16 @@ static int io_files_update(struct io_kiocb *req, unsigned int issue_flags)
 	return 0;
 }
 
+static int io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	return -EINVAL;
+}
+
+static int io_futex(struct io_kiocb *req, unsigned int issue_flags)
+{
+	return -EINVAL;
+}
+
 static int io_req_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	switch (req->opcode) {
@@ -5936,6 +5953,8 @@ static int io_req_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return io_renameat_prep(req, sqe);
 	case IORING_OP_UNLINKAT:
 		return io_unlinkat_prep(req, sqe);
+	case IORING_OP_FUTEX:
+		return io_futex_prep(req, sqe);
 	}
 
 	printk_once(KERN_WARNING "io_uring: unhandled opcode %d\n",
@@ -6203,6 +6222,9 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
 	case IORING_OP_UNLINKAT:
 		ret = io_unlinkat(req, issue_flags);
 		break;
+	case IORING_OP_FUTEX:
+		ret = io_futex(req, issue_flags);
+		break;
 	default:
 		ret = -EINVAL;
 		break;
@@ -10158,6 +10180,7 @@ static int __init io_uring_init(void)
 	BUILD_BUG_SQE_ELEM(28, __u32,  statx_flags);
 	BUILD_BUG_SQE_ELEM(28, __u32,  fadvise_advice);
 	BUILD_BUG_SQE_ELEM(28, __u32,  splice_flags);
+	BUILD_BUG_SQE_ELEM(28, __u32,  futex_flags);
 	BUILD_BUG_SQE_ELEM(32, __u64,  user_data);
 	BUILD_BUG_SQE_ELEM(40, __u16,  buf_index);
 	BUILD_BUG_SQE_ELEM(42, __u16,  personality);
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index e1ae46683301..6a1af5bb2ddf 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -44,6 +44,7 @@ struct io_uring_sqe {
 		__u32		splice_flags;
 		__u32		rename_flags;
 		__u32		unlink_flags;
+		__u32		futex_flags;
 	};
 	__u64	user_data;	/* data to be passed back at completion time */
 	union {
@@ -137,6 +138,7 @@ enum {
 	IORING_OP_SHUTDOWN,
 	IORING_OP_RENAMEAT,
 	IORING_OP_UNLINKAT,
+	IORING_OP_FUTEX,
 
 	/* this goes last, obviously */
 	IORING_OP_LAST,
@@ -174,6 +176,13 @@ enum {
 #define IORING_POLL_UPDATE_EVENTS	(1U << 1)
 #define IORING_POLL_UPDATE_USER_DATA	(1U << 2)
 
+enum {
+	IORING_FUTEX_WAKE_OP = 0,
+
+	IORING_FUTEX_LAST,
+};
+
+
 /*
  * IO completion data structure (Completion Queue Entry)
  */
-- 
2.31.1